Communities of Sound brings together insights from religion, anthropology, sound, and migration studies to explore the sonic traces of untouchability and forced migration across the Bay of Bengal. Based on an immersive, multi-sited ethnography with Matua devotees—a low-caste, Bengali-speaking Dalit religious community fragmented by Partition, war, and postcolonial displacement—the book explores how sound sustains identity across fractured geographies. Using richly detailed descriptions, the book follows traveling archives of song, story, and ritual performance through West Bengal, Bangladesh, and the Andaman Islands. These sonic practices—congregational singing, drumming, and itinerant storytelling—forge belonging beyond nation-states, connecting the Matua's fifty million members across borders and seas. In a world dominated by visual culture, Communities of Sound centers listening as a mode of knowledge and care, revealing how sound shapes our sense of self and cosmos. More than scriptures or doctrine, it is sound—entangled with authority and power—that binds this transregional Dalit movement and animates its collective action. The book is generously illustrated and references an online companion with video and audio examples.